Ok I'm nearly there. Still a few problems.
For some unseen reason I'm getting this error message, now I wasn't getting it earlier before I introduced the function buttons i.e + - \ * etc...
First of all I created another For loop, and another frame to house the function buttons. Esentially it was identical to the first for loop which created the buttons perfectly. But when I tried this loop I got the error message

 
Uncaught exception from user code:
Can't call method "Button" on an undefined value at C:\Documents and S
+ettings\Eoin\Desktop\calc.pl line 66.
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After that happened I tried to figure out what was wrong but I couldn't spot it, so Idecided to just use the first loop for all the buttons. So I introduced the extra buttons in the array and added in the part to make the + and = buttons bigger. I tested it and got the same error:

Uncaught exception from user code:
Can't call method "Button" on an undefined value at C:\Documents and S
+ettings\Eoin\Desktop\calc.pl line 52.
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I just don't understand it??
Heres the rest of it.

my $mw = new MainWindow(-title => 'Calc');
$mw->geometry("300x300");
my $topframe = $mw->Frame(-height => '60', -width => '300')->pack(-sid
+e => 'top', -expand => '0', -fill => 'x');
my $btmframe = $mw->Frame(-height => '225', -width => '300',)->pack(-s
+ide => 'left', -expand => '1', -fill => 'both');
push @rows, $btmframe->Frame()->pack( -expand => 1, -fill => 'both', -
+side => 'top') for (0..3);

my $display   =  $topframe->Entry(-justify      => 'right',
                                  -state        => 'disabled', 
                                  -textvariable => \$calc)
                           ->pack(-expand       => '1',
                                  -fill         => 'x',
                                  -pady         => 30,
                                  -padx         => 20,
                                  -side         => 'right');

$mw->bind("<KeyRelease>" , sub { &keypress } );


for my $i (
qw/
   7 8 9 * n*
   4 5 6 - \
   1 2 3 + =
   0 . C     / )
{

if($i eq '+' || $i eq '=')
{
$h = 2;
}

$button{$i} = $rows[$r]->Button(-text    => "$i", 
                                -width   => '3', 
                                -height  => "$h", 
                                -command => sub { &btnpress($i) })
                         ->pack(-expand  => 1,
                                -fill    => 'both',
                                -padx    => 2, 
                                -pady    => 2,
                                -side    => 'left',
                                -ipadx   => 5, 
                                -ipady   => 5);

$w++;
$h = 1;
if($w > 2){$w = 0; $r++;}
}



MainLoop;
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