in reply to extracting data from an input file and associated errors
You need to capture the match you want:
$line =~ m/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\.csv$/g
The match in your first set of parens will be stored in $1, in the second set of parens in $2, and so on.
See perldoc perlretut.
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Seekers of Perl Wisdom