http://www.perlmonks.org?node_id=1137215


in reply to Re: How to extract Name and No from .vcf file.
in thread How to extract Name and No from .vcf file.

How about command line parameter checking? 
...
my $filename = $ARGV[0];
my ($name, $number);

die "Usage: $0 filename\n" unless $filename; # checking command line p
+arameter
...

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