One thing you can add to his code if you only have one occurence of @user_info in the whole file is an exit from the loop as soon as you have found your data

That's a very good point! Here's two more variants, the first if the start and end tag should be captured, the second if they shouldn't (replaces the if/elsif):

    if ( my $flag = /\@user_info_start/ ... /\@user_info_end/ ) {
        push @userinfo, $_;
        last LINE if $flag=~/E0/;
    }

# - or -

    if ( my $flag = /\@user_info_start/ ... /\@user_info_end/ ) {
        last LINE if $flag=~/E0/;
        push @userinfo, $_ unless $flag==1;
    }
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See also Behavior of Flip-Flop Operators and Flipin good, or a total flop?