How do I perform a Perl substitution on a string while keeping the original?

regex perl replace
kaybenleroll picture kaybenleroll · Aug 22, 2008 · Viewed 198.7k times · Source

In Perl, what is a good way to perform a replacement on a string using a regular expression and store the value in a different variable, without changing the original?

I usually just copy the string to a new variable then bind it to the s/// regex that does the replacement on the new string, but I was wondering if there is a better way to do this?

$newstring = $oldstring;
$newstring =~ s/foo/bar/g;

Answer

John Siracusa picture John Siracusa · Aug 22, 2008

This is the idiom I've always used to get a modified copy of a string without changing the original:

(my $newstring = $oldstring) =~ s/foo/bar/g;

In perl 5.14.0 or later, you can use the new /r non-destructive substitution modifier:

my $newstring = $oldstring =~ s/foo/bar/gr;

NOTE:
The above solutions work without g too. They also work with any other modifiers.

SEE ALSO:
perldoc perlrequick: Perl regular expressions quick start

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