I'm acclimatizing to the "unix" way, and have found some situations where it's useful to process output of another command with pipes, through a custom perl script. Now, invoking the script with "perl -an" is often useful, I like it because it behaves in an intuitive way when dealing with pipes.

Now I have some little utilities built on "perl -an" that I would like to make more powerful by allowing flags to specify certain types of behavior. A simple example follows, where I'd like to select either letters or numbers from my piped output. Here, it doesn't work because I guess perl -an wants another file where I am trying to give it a flag.

Is there some way to do what I want with "perl -an" type invocation? Or do I have to use the diamond operator on STDOUT, like I was used to doing before I discovered perl -an?

Thanks... :) 

$cat input.txt | ./anWithArgs.pl letters # should spit out lines with 
+a letter
Can't open letters: Datei oder Verzeichnis nicht gefunden.
$cat input.txt | ./anWithArgs.pl numbers # should spit out lines with 
+a number
Can't open numbers: Datei oder Verzeichnis nicht gefunden.
$cat anWithArgs.pl
#!/usr/bin/perl -an

my $type = shift or die "no type";

if ( $type eq 'letters' ) {
  print if $_ =~ /\w/;
} elsif ( $type eq 'numbers' ) {
  print if $_ =~ /\d/;
} else {
  print "bad type: $type"
}
$cat input.txt
a
b
c
d
e
f
g
1
2
3
4
5
6
7
8
9

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In reply to custom args with perl -an type invocation? by tphyahoo

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