int( $string > 3 ) should be int( $string ) > 3.

You'll still get the warning unless you turn it off, though.

my $string = "1:00";
if ( do { no warnings qw( numeric ); int( $string ) } > 3 ) {
   say ">= 4";
} else {
   say "< 4";
}
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It would be clearer to use >= 4 than > 3. And if you do that, you don't even need int.

my $string = "1:00";
if ( do { no warnings qw( numeric ); $string >= 4 } ) {
   say ">= 4";
} else {
   say "< 4";
}
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