Hallo

Der Vollständigkeit halber:
perldoc -f select

You can effect a sleep of 250 milliseconds this way:

select(undef, undef, undef, 0.25);

Note that whether "select" gets restarted after signals (say,
SIGALRM) is implementation-dependent. See also perlport for
notes on the portability of "select".

Gruß
Kristian