in reply to Re^4: REGEX omit dashes - simple but ...
in thread REGEX omit dashes - simple but ...

You are getting an uninitialized error because you are trying to change the content of $access_num, to which you've assigned $1, but there were no parentheses in your first regular expression. Maybe you mean something like:
if ($line =~ s/^\s*ACCESSION\s*NUMBER:\s*/) { $line =~ tr/-//; }
or possibly
if ($line =~ s/^\s*ACCESSION\s*NUMBER:\s*([-\d]+)$/m) { $access_num = $1; $access_num =~ tr/-//; }

#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.