You could turn GrandFather's approach around and swap keys and values in the hash: 
my %data;
( $data{ $_}) =  /^\d+\s+(\d+)/ while <DATA>;

print for sort { $data{ $a} cmp $data{ $b} } keys %data;

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This is essentially a variant of the Schwartz Transform, using a hash in place of an array to keep the sort field(s).

Anno

In reply to Re^3: Sorting a text file by Anno
in thread Sorting a text file by rsriram

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