Try escaping the dollar sign. You're probably having an issue with Perl interpreting $GPGLL as a scalar. Since it's undefined, you have a problem. Also, make sure you turn on warnings and strict. That will catch problems like that.

#!/usr/bin/perl -w
use strict;

my $var = "$GPGLL,577.015,N,01201.076,E,"; #wrong!

or

my $var = "\$GPGLL,577.015,N,01201.076,E,"; #better.  Note the escape.

or

my $var = '$GPGLL,577.015,N,01201.076,E,';
[download]

In the final example, single quotes are used. Double quotes around a string allow for variable interpolation. Single quotes prevent that. There are a variety of ways that your code could have issues with interpolation. If you post a small snippet, we can take a look and figure out exactly how it is occurring.

Cheers,
Ovid

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