$line[0]="12/123 11-abc 456 a 1/2 zyx this is the last";
$line[1]="14/456 11-abc 456 a 1/2 zyx this is it";

for (@line)
{
        if(m|(\d+/123 11-[a-z]+ \d+)|g)
        {
                $start=$1;
                /\G(.*?) zyx (.*)$/;
                print "Start of record:$start\nBefore zyx:$1\nand After zyx:$2\n";
        }
}

__OUTPUT__

Start of record:12/123 11-abc 456
Before zyx: a 1/2
and After zyx:this is the last