update:
It appears that my initial regex attempt did not yield the desired result.
In an effort to rectify this, I present two alternative solutions that have been verified to work -
1.
Implementation of Multi-Line mode - This method utilizes the \G anchor to ensure a well-formatted and concise output suitable for array manipulation.
# '/(^Fig[a-zA-Z.]*\h+|(?!^)\G)(?(?<=\d)\h*,\h*)(\d+)(?|\h*(-)\h*(\d+)|\h+(and)\h+(\d+)|\h+(to)\h+(\d+))?/'
( # (1 start)
^ Fig [a-zA-Z.]* \h+ # Fig's
| # or,
(?! ^ ) # Start at the end of last match
\G
) # (1 end)
(?(?<= \d ) # Conditional, if previous digit
\h* , \h* # Require a comma
) # End conditional
(\d+) # (2), Digit
(?| # Branch reset (optionally, one of the (-|and|to) \d forms)
\h*
( - ) # (3), '-'
\h*
( \d+ ) # (4), Digit
| \h+
( and ) # (3), 'and'
\h+
( \d+ ) # (4), Digit
| \h+
( to ) # (3), 'to'
\h+
( \d+ ) # (4), Digit
)?
Perl test scenario
$/ = undef;
$str = <DATA>;
while ($str =~ /(^Fig[a-zA-Z.]*\h+|(?!^)\G)(?(?<=\d)\h*,\h*)(\d+)(?|\h*(-)\h*(\d+)|\h+(and)\h+(\d+)|\h+(to)\h+(\d+))?/mg)
{
length($1) ?
print "'$1'\t'$2'\t'$3'\t'$4'\n" :
print "'$1'\t\t'$2'\t'$3'\t'$4'\n" ;
}
__DATA__
Figs. 1, 2, 3 and 4
Figures 1, 2
Figs. 1 and 2
Figure 1-3
Figure 1 to 3
Figure 1
Result >>
'Figs. ' '1' '' ''
'' '2' '' ''
'' '3' 'and' '4'
'Figures ' '1' '' ''
'' '2' '' ''
'Figs. ' '1' 'and' '2'
'Figure ' '1' '-' '3'
'Figure ' '1' 'to' '3'
'Figure ' '1' '' ''
2. Utilizing Multi-Line mode - This pattern captures entire lines, with group 1 containing 'Figs',
group 2 encompassing all numerical representations
# '/^(Fig[a-zA-Z.]*\h+)((?(?<=\d)\h*,\h*|\d+(?:\h*-\h*\d+|\h+and\h+\d+|\h+to\h+\d+)?)+)\h*$/'
^
(Fig [a-zA-Z.]* \h+ ) # (1), Fig's
( # (2 start), All the num's
(?(?<= \d ) # Conditional, if previous digit
\h* , \h* # Require a comma
| # or
\d+ # Require a digit
(?: # (and optionally, one of the \d (-|and|to) \d forms)
\h* - \h* \d+
| \h+ and \h+ \d+
| \h+ to \h+ \d+
)?
)+
) # (2 end)
\h*
$