while (my @parsed = &parseInput) {
    &dispatch(@parsed);
}

sub parseInput {
    ...
    my @parsed = split $inp;
    return 0 if $parsed[0] eq `q`;
    ...
}
[download]

The expression  $parsed[0] eq `q` (backticks) will try to get the system to do  qx{q} and then compare  $parsed[0] against the value returned from the system; it will probably never be true. The statement should probably be
    return 0 if $parsed[0] eq 'q';
or perhaps better yet
    return 0 if lc($parsed[0]) eq 'q';
(Update: See also the note about split in Update 2 below.)

But (Update: anonymized user 468275 has since changed the statement in question to return an empty list.)
    return 0 if $parsed[0] eq 'q';
still has a problem because it returns a non-empty list if the condition is true, and the while-loop test
    while (my @parsed = &parseInput) { ... }
will be true because  @parsed is not empty, so  &dispatch(@parsed) will be called with a  (0) argument list. Probably better to use the statement
    return if lc($parsed[0]) eq 'q';
because that will return an empty list and cause the while-loop to terminate.

sub dispatch {
    my $cmd = shift;
    try { eval( '&' . $cmd . '(' . join ',', @_ . ');' ); }
    catch { print STDERR "Unrecognised command $cmd\n"; }
    # the above is a non-GUI example which would need adaptation      
}
[download]

This looks to me like a bad idea because it seems to offer an injection point for user supplied input — code! (Update: See also the note about building the string for eval in Update 3 below.) Better IMHO to use a dispatch table:

c:\@Work\Perl\monks>perl -wMstrict -le
"BEGIN {
   ;;
   my %dispat = (
     'foo' => sub { print 'Fooing: ', qq{(@_)}; },
     'bar' => \&bar,
     );
   ;;
   sub dispatch {
     my $cmd = shift;
     ;;
     $cmd = lc $cmd;
     if (not exists $dispat{$cmd}) {
       print qq{do not know how to '$cmd'};
       return;
       }
     $dispat{$cmd}->(@_);
     }
   }
 ;;
 while (my @parsed = parseInput()) {
   dispatch(@parsed);
   }
 ;;
 sub parseInput {
   my $inp = <>;
   chomp $inp;
   my @parsed = split ' ', $inp;
   return if lc($parsed[0]) eq 'q';
   return @parsed;
   }
 ;;
 sub bar { print 'Baring: ', qq{(@_)}; }
"
foo
Fooing: ()
bar
Baring: ()
foo 1 2 3
Fooing: (1 2 3)
bar x xyzzy
Baring: (x xyzzy)
boff
do not know how to 'boff'
Q
[download]

Update 1: Several minor wording changes; formatting adjustment to the code example.

Update 2: The statement
    my @parsed = split $inp;
in the OPed code | code here is incorrect because it calls split with a split pattern of  $inp on the (as-yet uninitialized) string in  $_

Update 3: Sorry to seem like piling on, but the statement
    eval( '&' . $cmd . '(' . join ',', @_ . ');' );
is also problematic. The scalar concatenation of  @_ with another string will evaluate the array in scalar context, i.e., as the number of elements in the array. The problem is easily fixed by a couple more parentheses (if you really want to dance with the Devil by the pale moonlight):

c:\@Work\Perl\monks>perl -wMstrict -le
"dispatch(qw(foo 9 8 7 6));
 ;;
 sub dispatch {
   my $cmd = shift;
   my $evil_string = '&' . $cmd . '(' . join ',', @_ . ');';
   print qq{>>$evil_string<<};
   }
"
>>&foo(4);<<

c:\@Work\Perl\monks>perl -wMstrict -le
"dispatch(qw(foo 9 8 7 6));
 ;;
 sub dispatch {
   my $cmd = shift;
   my $evil_string = '&' . $cmd . '(' . join(',', @_) . ');';
   eval $evil_string;
   }
 ;;
 sub foo { print qq{'in Foo:' (@_)} }
"
'in Foo:' (9 8 7 6)
[download]

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