Looping over data
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Perl provides a few ways to loop over data and manipulate it. Let's say you want to just print the lines of a file that match a regex but prefix it with some string. You might start with a perl program like:
#!/usr/bin/perl
open( IN, $ARGV[0] );
while( $line = <IN> ) {
print "** $line" if $line =~ /^\d+/;
}
close( IN );
This will print all lines that start with numbers, and prefix the line with some "&"'s. Now this would be way too much to type at a prompt, but perl has a switch to eliminate the whole while loop, so all you're left with is the print statement, so you could do it like this:
perl -ne 'print "** $_" if /\d+/' myfile.txtThe -n means wrap the script in while(<>){} and the -e means to execute the next part instead of using a script file, so myfile.txt isn't considered a script, it's the input data. Read up on different switches in the perlrun man page.