join() in print()

Answer

print LIST;

is slower than

print join '', LIST;

Perl calls Perl_do_print() for every item in the list resulting in one system-call per list element. This is even true for arrays, so perl will not translate

print @ARY;

into

print join $,, @ARY;

In fact, it will print the array in a particularly wasteful way, namely:

for (0 .. $#ARY) {
  print $ARY[$_];
  print $, if $_ < $#ARY;
}