Your problem lies here: my $substitute = qq{throw \("$1"\)};

Using qq makes Perl interpolate variables which means that the current value of $1 (at this place undef) is inserted.

Update:
Well, typical, sorry, didn't double check what I wrote (and deleted now :). You have to use the following trick to achieve what you want: 

my $substitute = q{qq{throw ("$1")}};

# and later substitute like this
$line =~ s/$regex/$substitute/ee;

[download]
The reason for this is that perl is not automatically doing an interpolation on the substitution string you insert. You have to force that by evalutating before substitution.

-- Hofmator

In reply to Re: Execute regexp on directory tree by Hofmator
in thread Execute regexp on directory tree by karmas

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