re = /SSR.(....)(.BE.)(\w+)(-1)(\w+)(\/)(\w+).*/m
str = 'SSR BAGW BE HK1DUBEXT0304H13OCT-1TIMBRELL/TEGAELAMISS.1P/AUTH 23KG
SSR BAGA BE HK1DUBLON0301H13NOV-1TIMBRELL/TEGAELAMISS.1P/AUTH 23KG
SSR DOCS BE HK1DUBEXT0204H13DEC-1TIMBRELL/TEGAELAMISS
SSR PETC BE HK1LONEXT0334H13JAN-1TIMBRELL/TEGAELAMISS
SSR WCHR BE HK1DUBEXT0204H13DEC-1TIMBRELL/TEGAELAMISS
SSR BAGW BE HK1DUBLON0301H13NOV-1TIMBRELL/TEGAELAMISS.1P/AUTH 23KG
BE7351 H 08NOV18MANMXP HK4/11251440
BE2108R/VS8508Y 11NOV18LHREDI HK10/18202000
A97351 H 08NOV18MANMXP HK4/11251440'
subst = '\\1-\\5-\\7'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html