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Regular Expressions

Expand variables in single-quoted strings / user input by KevinADC
Posted: 3 Feb 07 (Edited 15 Feb 07)

----------------------------
ignore this section:
code
perl
print

----------------------------


Perl will only expand variables in double-quoted strings. Using a bit a 'magic' you can get perl to expand variables in single-quoted strings as well. This can come in handy for expanding variables in a text file, or user input, or other data:

CODE

my $lamb = 'wolf';
my $text = 'Mary had a little $lamb.';
$text =~ s/(\$\w+)/$1/eeg;
print $text;

This is genuine variable interpolation, not substitution of one pattern for another. Using the 'e' modifier (you have to use two like in the example for lexical variables) perl will evaluate the replacement pattern as code.

If you are not using "strict" (shame on you) you can use symbolic dereferencing:

CODE

my $lamb = 'wolf';
my $text = 'Mary had a little $lamb.';
$text =~ s/\$(\w+)/${$1}/g;
print $text;

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