You cannot modify number variables. Make a copy first: 
while ($text =~ m/(TATAAT|TTGACAT)\w+[^ATG]?(ATG\w+)[^TAG|TAA|TGA]?/g)
+ {
    my $match = $2;
    $match =~ tr/ATGC/UACG/;
    print $match;
}

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In reply to Re: Modification of read only values. by JavaFan
in thread Modification of read only values. by Ekolet

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