while ( not defined $result ) {
    ( $result = try( $something ) ) or sleep 3;
}

##</code><code>##

while ( not defined $result ) {
    ( $result = try( $something ) )
        or select undef, undef, undef, 3000;
}

##</code><code>##

use Time::HiRes qw/ usleep /;

while( not defined $result ) {
    ( $result = try( $something ) ) or usleep( 3000 );
}