Use more whitespace (blank lines) and indentation to separate each bit of code - you don't have to but it makes things much easier to identify ... this is all - of course - up to the individual person... but if I were to do this I would have formatted it like so ...

print("\n\nEnter a binary number:");
chomp($binary=<STDIN>);


if ( $binary =~/\D.*/ ) { 
    print("Not a binary number!\n");
    exit;
    }


if ( $binary =~/\d.*/ ) { 

    @eachnum = split (//, $binary);
    $good = 1;
    
    foreach (@eachnum){
        next if /0/ || /1/;
        print("A binary number contains 1's and 0's!\n");
        $good = 0;    
        last;    
    }

    if ( $good == 1 ) {
           convb2d();
    }
}
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-mr.dunstan