sleep can only sleep for an integer amount of time. Essentially, anything you pass to sleep will seem as though you did sleep( int(###) );. So sleep( 2.5 ) will sleep for 2 seconds, not 2.5. There are two solutions: use select as davido says (select( undef, undef, undef, 2.5 )) or else pull in the Time::HiRes module to replace the sleep command with one that works with floating point sleep times:

use Time::HiRes qw( sleep );

sleep( 2.5 );
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