Thanks everyone for all the insights. As it turned out, just converting it to oct, as waldner suggested, worked the easiest. Other solutions seemed to lop off leading 0's or for whatever reason would not be accepted by Gtk2 as hex. If I hard code a number with a leading 0x it would accept it, but it wouldn't accept any 0x in a variable.... it had to be converted to a oct or decimal number. 
#!/usr/bin/perl

my $x = 0;
my $y = 0;
my $z = 255;

my $hex = sprintf( "0x%02x%02x%02x40",$x,$y,$z); 
print "$hex\n";

#works
   print "hex  $hex\n";
   my $oct = oct $hex;
   print  "oct $oct\n";   
#   $rect->set('fill-color-rgba' => $oct );


# works as hex, but leading 0x not acceptable to Gtk2 
my $hex1 = sprintf "0x%08x", $oct; 
print "hex1  $hex1\n";
 #$rect->set('fill-color-rgba' => $hex1 ); # pukes on the 0x
# would work if I eval'd $hex1, which converted it to decimal

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In reply to Re: convert hex string to hex number by zentara
in thread convert hex string to hex number by zentara

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