re = /"(?=(?:(?:[^<](?!%>))*(?:<%[^%]+%>)(?:[^<](?!%>))*)*$)/
str = 'select "SomethingQuoted", "SomethingQuoted" , "SomethingQuoted" , "SomethingQuoted" to_char(max(decode( landing_name,\'DX_L_MDC_RDM\', BATCH_ID , -1))) as MDC_RDM_BATCH_ID
,to_char(max(decode( landing_name,\'DX_L_ESB_SPARK\', BATCH_ID , -1))) as ESB_SPARK_BATCH_ID
from (
select max(u.batch_id) as BATCH_ID , u.landing_name
from "<%=odiRef.getSchemaName("DJC_METADATA","D")%> .u$dx_batch_log u
"SomethingQuoted"
join <%=odiRef.getSchemaName("DJC_METADATA","D")%> .djc$dx_landing la
on u.landing_name = la.landing_name
and u.batch_id >= la.last_deleted_batch_id
join <%=odiRef.getSchemaName("DJC_METADATA","D")%> .djc$load_log lo
on u.load_id = lo.load_id
and lo.status = \'COMPLETE\'
and lo.load_id > 0
"SomethingQuoted"
"SomethingQuoted"
where u.landing_name in (\'DX_L_MDC_RDM\', \'DX_L_ESB_SPARK\')
and u.chkp_status = \'FINISHED\'
group by u.landing_name
) "<%==" "=%>
'
subst = '#'
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