Use variable as RegEx pattern

Question

I'd like to use a variable as a RegEx pattern for matching filenames:

my $file = "test~"; my $regex1 = '^.+\Q~\E$'; my $regex2 = '^.+\\Q~\\E$'; print int($file =~ m/$regex1/)."\n"; print int($file =~ m/$regex2/)."\n"; print int($file =~ m/^.+\Q~\E$/)."\n"; 

The result (or on ideone.com):

0 0 1 

Can anyone explain to me how I can use a variable as a RegEx pattern?

Answer 1

As documentation says:

    $re = qr/$pattern/;     $string =~ /foo${re}bar/; # can be interpolated in other patterns     $string =~ $re; # or used standalone     $string =~ /$re/; # or this way 

So, use the qr quote-like operator.

Answer 2

You cannot use \Q in a single-quoted / non-interpolated string. It must be seen by the lexer.

Anyway, tilde isn’t a meta-character.

Add use regex "debug" and you will see what is actually happening.