Put my on the loop variables: 
foreach my $oldkey (keys %fdat) {
    if ( (my $newkey = $oldkey) =~ s/^redirect_//) {
        $fdat{$newkey} = $fdat{$oldkey};
    }
}

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That way you know you won't accidentally conflict with any globals of the same name. And it will pass the handy-dandy spell-checker known as strict.

In reply to Re (tilly) 1: Regexs on Hash Keys by tilly
in thread Regexs on Hash Keys by Maclir

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