#!/usr/bin/perl
use warnings;

# can be simplified to just #!/usr/bin/perl -w
# this will work even on Windows!! Windows Perl doesn't look 
# at the path, but it does look at the -w trailing thing.

You will see this often at the start of a Perl program:
#!/usr/bin/perl -w
use strict;

##</code><code>##

sub A
{
  my $parm1 = shift;  #effect: literally shift off the stack passed
}

sub B
{
  my ($p1,$p2,$p3) = @_; #effect: make copy from stack passed
}

##</code><code>##

while ( (print "Enter Command: "), 
        (my $line = <STDIN>) !~ /^\s*q(uit)?\s*$/i  
      )
{
   next   if $line =~ /^\s*$/;        #skip new lines
   next   if $line =~/^\s*skip/i;     #skip is a no op command
   insert if $line =~/^\s*insert/i;   #do insert command
   delete if $line =~/^\s*delete/i;   #do delete command
   #...etc..
}
sub insert()
{...}
sub delete()
{...}