You're not taking into account the non-greediness. To accommodate matching the $ (which is before the newline) $1 holds 'foo'. If you also want to match the terminal newline, use \z instead of $: 

$ perl -e '$_="foo\n"; print "1=|$1|\n" if m/(fo.+?)$/s'
1=|foo|

$ perl -e '$_="foo\n"; print "1=|$1|\n" if m/(fo.+?)\z/s'
1=|foo
|

[download]

Your comparison with the first one-liner is not comparing apples with apples: 

$ perl -e '$_="foo\nbar"; print "1=|$1|\n" if m/(fo.+?)$/s'
1=|foo
bar|

$ perl -e '$_="foo\nbar\n"; print "1=|$1|\n" if m/(fo.+?)$/s'
1=|foo
bar|

$ perl -e '$_="foo\nbar\n"; print "1=|$1|\n" if m/(fo.+?)\z/s'
1=|foo
bar
|

[download]

I also second ++Fletch's recommendation to use Regexp::Debugger. This allows you to step through the matching process and see exactly what's happening. I often use it myself.

— Ken

In reply to Re^3: Non-greedy match end of line bug? by kcott
in thread Non-greedy match end of line bug? by am12345

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