You can use the %b template in printf: 
my $int = 123;
printf "%b\n", $int;

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Update: Another option is to use pack + unpack. 

my $int = 123;
say unpack "B*", pack "n", $int;

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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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In reply to Re: convert to binary number by choroba
in thread convert to binary number by Anonymous Monk

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