perlman root The section of the FAQ answers question related to the manipulation of data as numbers, dates, strings, arrays, hashes, and miscellaneous data issues. Data: Numbers <UL> [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 bits into ints?] [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?] [Why aren't my random numbers random?] </UL> Data: Dates<UL> [How do I find the week-of-the-year/day-of-the-year?] [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?] [Does Perl have a year 2000 problem? Is Perl Y2K compliant?] </UL> Data: Strings <UL> [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/change the first N letters 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 do I strip blank space from the beginning/end of a string?] [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?] </UL> Data: Arrays<UL> [What is the difference between $array[1] and @array[1]?] [How can I extract just the unique elements of an array?] [How can I tell whether a list or array contains a certain element?] [How do I compute the difference of two arrays? How do I compute the intersection of two arrays?] [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?] </UL> Data: Hashes(Associative Arrays)<UL> [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 can I use a reference as a hash key?] </UL> Data: Misc <UL> [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?] </UL>