Read through a file and pick out lines that contain one of a number of "trigger" strings. Print the lines grouped by the string they matched, then print the remaining lines.

linesort.pl

#!/usr/bin/perl -w

# Read through a file and pick out lines that contain one of a number of 
# "trigger" strings. Print the lines grouped by the string they matched, then 
# print the remaining lines. 
# 
# Usage: linesort.pl myfile.txt

use File::Slurp;
use Array::Each qw( rewind );
use strict;

# These are the trigger strings we are looking for
my @triggers = ('foo', 'bar', 'baz');

# Read in the lines from the file given on the command line
my @lines = read_file( $ARGV[0] );
# An array for temporarily holding lines that did not contain a match
my @tmp;

foreach my $trigger ( @triggers ) {

  print "\n*** $trigger\n";

  while ( my $line = shift @lines ) {
    if ($line =~ m/$trigger/) {
      print $line;
    } else {
      # Assign the lines that did not contain a match to a temporary array so 
      # we don't forget them, but can try them with another trigger word
      push @tmp, $line;
    }
  }
  # Assign the lines that did not contain a hit this time to the original array
  # so we can have another go at it
  @lines = @tmp;
  # Make sure the temporary array is empty
  @tmp = ();

}

# Print out the remaining lines
print "\n\n*** The rest\n", @lines;