Use a signal handler?:

{ 
    local $SIG{__WARN__} = sub { print "Bad line: '$_'"; return; };  
    for( qw[ 1 2 3 d 5 f 6 ] ) { 
        print $_ * 2; 
    } 
};;
2
4
6
Bad line: 'd'
0
10
Bad line: 'f'
0
12
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