Assuming that mean push a scalar onto an arrayref already contained within an array element, (as opposed to pushing an arrayref onto an array as the other respondents have demonstrated), then: 

@a = ( [1, 2.3 ], ['a'..'c'], ['p'..'r']);;
pp \@a;;

[[1, "2.3"], ["a", "b", "c"], ["p", "q", "r"]]

push @{ $a[ 1 ] }, 'a scalar';;
pp \@a;;

[[1, "2.3"], ["a", "b", "c", "a scalar"], ["p", "q", "r"]]

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In reply to Re: Push into an array inside a array by BrowserUk
in thread Push into an array inside a array by baski

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