regex101: PCRE (Legacy) Match Workspace

Regular Expression

^
(                    # let's start capturing
 .*		             # if there's something before the two words
 (?:
  (?=\bfoo\b)\w+     # match the first word
  .*                 # if there's something in the middle of the two words
  (?=\bbar\b)\w+     # match the second word
  |                  # OR let's do everything above but in reverse this time
  (?=\bbar\b)\w+
  .*
  (?=\bfoo\b)\w+
 )
 .*                 # if there's something after the two words
)
$

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z

Substitution

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z test foo foo bar

Y => yy bar z fo oxxx

N => aa foobb bar

N => xx bar xfoo

Y => foo xxx ba   z