use strict;
use warnings;

my $item                  = "SeaMonkeys";
my $catNum                = "SMKY-1978";
my $remainingToReplace = 2;
my @lines;

local $/ = "\n\n";
while (defined (my $block = <DATA>)) {
    @lines = split "\n", $block;
    next unless $remainingToReplace;
    next unless $lines[0] =~ m/\Q$item\E/;

    # Replacement needed here
    print "***** Found $item, counter $remainingToReplace *****\n";
    --$remainingToReplace;

} continue {
    print join "\n", @lines, "\n";
}

__DATA__
Data per OP's node