Try:

use feature ":5.14";
use warnings FATAL => qw(all);
use strict;

for(split /\n/, << 'END')
jay 21 34 56
bob 12 39
jay 11 10
bob 14
jay 190
bob 13
END
 {s/jay/bob/ or s/bob/jay/;
  say
 }
[download]

Produces

bob 21 34 56
jay 12 39
bob 11 10
jay 14
bob 190
jay 13