Beginning Web Development With Perl : From Novice to ... - Nabo

292APPENDIX ■ PERL BASICSBy default, a here-document works like a double-quoted string. In order for it to work likea single-quoted string, surround the label in single quotes. This will become important whenvariable interpolation comes into play, as you’ll see later on.Converting Between Numbers and StringsPerl treats numbers and strings on an equal footing, and where necessary, Perl convertsbetween strings, integers, and floating-point numbers behind the scenes. There is a specialterm for this: automatic conversion of scalars. This means that you don’t have to worry aboutmaking the conversions yourself, like you do in other languages. If you have a string literal"0.25" and multiply it by 4, Perl treats it as a number and gives you the expected answer, 1. Forexample:#!/usr/bin/perl -w# autoconvert.plprint "0.25" * 4, "\ n";The asterisk (*) is the multiplication operator. All of Perl’s operators, including this one,are discussed in the next section.There is, however, one area where this automatic conversion does not take place. Octal,hex, and binary numbers in string literals or strings stored in variables don’t get convertedautomatically.#!/usr/bin/perl -w# octhex1.plprint "0x30\ n";print "030\ n";gives you$ perl octhex1.pl0x30030$If you ever find yourself with a string containing a hex or octal value that you need to convertinto a number, you can use the hex() or oct() functions accordingly:#!/usr/bin/perl -w# octhex2.plprint hex("0x30"), "\ n";print oct("030"), "\ n";This will now produce the expected answers, 48 and 24. Note that for hex() or oct(), theprefix 0x or 0, respectively, is not required. If you know that what you have is definitely supposedto be a hex or octal number, then hex(30) and oct(30) will produce the precedingresults. As you can see from that, the string "30" and the number 30 are treated as the same.