About dieing in Perl - Perl example

An Introduction to Standards in Perl example from a Well House Consultants training course
More on An Introduction to Standards in Perl [link]

This example is described in the following article(s):
• About dieing and exiting in Perl - [link]

Source code: chink Module: P711

=head1

If you want to end a program in Perl, you can get
out quickly enough with an exit function call.
But that's probably just a part of what you'll be wanting
to do - you'll be wanting to generate an error message
on the error channel (STDERR) too, and perhaps to tell
your user rather more about why the program died.

The die function provides a message on STDERR and
the exits your program. If you add a \n on as the last
character, it will NOT tell you the line number in your
code where it died, but with the \n it does tell you.

Note that if you have your die function tell you the
line number, it will also tell you how many lines have
been read from the latest file. At first, this will
seem odd but it's very useful indeed in helping to
identify which line of a long data file caused your
program to halt!

Some useful variables to use within die strings:
$0 - program name
$. - number of lines of data read in
$! - error message from open function

=cut

@ARGV < 2 and die ("Usage: $0 perlregex filename\n");
($lookfor, $file) = @ARGV;
open (FH,$file) or die ("$0: Input file $file problem\n$!");
while (<FH>) {
        if (/$lookfor/)
                {die("Data trap");}
        }
print "Completed Correctly\n";

__END__

Sample output:

Dorothy:p82 grahamellis$ perl chink
Usage: chink perlregex filename
Dorothy:p82 grahamellis$ perl chink Java ../requst.xyz
chink: Input file ../requst.xyz problem
No such file or directory at chink line 33.
Dorothy:p82 grahamellis$ perl chink Java ../requests.xyz
Data trap at chink line 35, <FH> line 2.
Dorothy:p82 grahamellis$ perl chink Javascript ../requests.xyz
Completed Correctly
Dorothy:p82 grahamellis$

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