|
• |
|
Why am I getting long decimals
(eg, 19.9499999999999) instead of the numbers I should be
getting (eg, 19.95)? |
|
• |
|
Why isn’t my octal data interpreted correctly? |
|
• |
|
Does Perl have a round() function? What about
ceil() and floor()? Trig functions? |
|
• |
|
How do I convert between numeric representations? |
|
• |
|
Why doesn’t & work the way I want it to? |
|
• |
|
How do I multiply matrices? |
|
• |
|
How do I perform an operation on a series of
integers? |
|
• |
|
How can I output Roman numerals? |
|
• |
|
Why aren’t my random numbers random? |
|
• |
|
How do I get a random number between X and Y? |
|
• |
|
How do I find the day or week of the year? |
|
• |
|
How do I find the current century or millennium? |
|
• |
|
How can I compare two dates and find the difference? |
|
• |
|
How can I take a string and turn it into epoch
seconds? |
|
• |
|
How can I find the Julian Day? |
|
• |
|
How do I find yesterday’s date? |
|
• |
|
Does Perl have a Year 2000 problem? Is Perl Y2K
compliant? |
|
• |
|
How do I validate input? |
|
• |
|
How do I unescape a string? |
|
• |
|
How do I remove consecutive pairs of characters? |
|
• |
|
How do I expand function calls in a string? |
|
• |
|
How do I find matching/nesting anything? |
|
• |
|
How do I reverse a string? |
|
• |
|
How do I expand tabs in a string? |
|
• |
|
How do I reformat a paragraph? |
|
• |
|
How can I access or change N characters of a string? |
|
• |
|
How do I change the Nth occurrence of something? |
|
• |
|
How can I count the number of occurrences of a substring
within a string? |
|
• |
|
How do I capitalize all the words on one line? |
|
• |
|
How can I split a [character] delimited string except
when inside [character]? |
|
• |
|
How do I strip blank space from the beginning/end of a
string? |
|
• |
|
How do I pad a string with blanks or pad a number with
zeroes? |
|
• |
|
How do I extract selected columns from a string? |
|
• |
|
How do I find the soundex value of a string? |
|
• |
|
How can I expand variables in text strings? |
|
• |
|
What’s wrong with always quoting
"$vars"? |
|
• |
|
Why don’t my << HERE
documents work? |
|
• |
|
What is the difference between a list and an array? |
|
• |
|
What is the difference between $array[1] and
@array[1]? |
|
• |
|
How can I remove duplicate elements from a list or
array? |
|
• |
|
How can I tell whether a certain element is contained in
a list or array? |
|
• |
|
How do I compute the difference of two arrays? How do I
compute the intersection of two arrays? |
|
• |
|
How do I test whether two arrays or hashes are
equal? |
|
• |
|
How do I find the first array element for which a
condition is true? |
|
• |
|
How do I handle linked lists? |
|
• |
|
How do I handle circular lists? |
|
• |
|
How do I shuffle an array randomly? |
|
• |
|
How do I process/modify each element of an array? |
|
• |
|
How do I select a random element from an array? |
|
• |
|
How do I permute N elements of a list? |
|
• |
|
How do I sort an array by (anything)? |
|
• |
|
How do I manipulate arrays of bits? |
|
• |
|
Why does defined() return true on empty arrays
and hashes? |
|
• |
|
How do I process an entire hash? |
|
• |
|
What happens if I add or remove keys from a hash while
iterating over it? |
|
• |
|
How do I look up a hash element by value? |
|
• |
|
How can I know how many entries are in a hash? |
|
• |
|
How do I sort a hash (optionally by value instead of
key)? |
|
• |
|
How can I always keep my hash sorted? |
|
• |
|
What’s the difference between "delete"
and "undef" with hashes? |
|
• |
|
Why don’t my tied hashes make the defined/exists
distinction? |
|
• |
|
How do I reset an each() operation part-way
through? |
|
• |
|
How can I get the unique keys from two hashes? |
|
• |
|
How can I store a multidimensional array in a
DBM file? |
|
• |
|
How can I make my hash remember the order I put elements
into it? |
|
• |
|
Why does passing a subroutine an undefined element in a
hash create it? |
|
• |
|
How can I make the Perl equivalent of a C structure/C
++ class/hash or array of hashes or
arrays? |
|
• |
|
How can I use a reference as a hash key? |
|
• |
|
How do I handle binary data correctly? |
|
• |
|
How do I determine whether a scalar is a
number/whole/integer/float? |
|
• |
|
How do I keep persistent data across program calls? |
|
• |
|
How do I print out or copy a recursive data
structure? |
|
• |
|
How do I define methods for every class/object? |
|
• |
|
How do I verify a credit card checksum? |
|
• |
|
How do I pack arrays of doubles or floats for
XS code? |
I/O and the
"f" issues: filehandles, flushing, formats, and
footers.
|
• |
|
How do I flush/unbuffer an
output filehandle? Why must I do this? |
|
• |
|
How do I change one line in a file/delete a line in a
file/insert a line in the middle of a file/append to the
beginning of a file? |
|
• |
|
How do I count the number of lines in a file? |
|
• |
|
How can I use Perl’s "-i"
option from within a program? |
|
• |
|
How do I make a temporary file name? |
|
• |
|
How can I manipulate fixed-record-length files? |
|
• |
|
How can I make a filehandle local to a subroutine? How
do I pass filehandles between subroutines? How do I make an
array of filehandles? |
|
• |
|
How can I use a filehandle indirectly? |
|
• |
|
How can I set up a footer format to be used with
write()? |
|
• |
|
How can I write() into a string? |
|
• |
|
How can I output my numbers with commas added? |
|
• |
|
How can I translate tildes (~) in a filename? |
|
• |
|
How come when I open a file read-write it wipes it
out? |
|
• |
|
Why do I sometimes get an "Argument list too
long" when I use <*>? |
|
• |
|
Is there a leak/bug in glob()? |
|
• |
|
How can I open a file with a leading ">" or
trailing blanks? |
|
• |
|
How can I reliably rename a file? |
|
• |
|
How can I lock a file? |
|
• |
|
Why can’t I just open( FH ,
">file.lock")? |
|
• |
|
I still don’t get locking. I just want to
increment the number in the file. How can I do this? |
|
• |
|
All I want to do is append a small amount of text to the
end of a file. Do I still have to use locking? |
|
• |
|
How do I randomly update a binary file? |
|
• |
|
How do I get a file’s timestamp in perl? |
|
• |
|
How do I set a file’s timestamp in perl? |
|
• |
|
How do I print to more than one file at once? |
|
• |
|
How can I read in an entire file all at once? |
|
• |
|
How can I read in a file by paragraphs? |
|
• |
|
How can I read a single character from a file? From the
keyboard? |
|
• |
|
How can I tell whether there’s a character waiting
on a filehandle? |
|
• |
|
How do I do a "tail -f" in perl? |
|
• |
|
How do I dup() a filehandle in Perl? |
|
• |
|
How do I close a file descriptor by number? |
|
• |
|
Why can’t I use "C:\temp\foo" in
DOS paths? What doesn’t
’C:\temp\foo.exe’ work? |
|
• |
|
Why doesn’t glob("*.*") get all the
files? |
|
• |
|
Why does Perl let me delete read-only files? Why does
"-i" clobber protected files? Isn’t
this a bug in Perl? |
|
• |
|
How do I select a random line from a file? |
|
• |
|
Why do I get weird spaces when I print an array of
lines? |